A new approach to comprehensively evaluate the morphological properties of the human femoral head: example of application to osteoarthritic joint

Abstract

Osteoarthritis affects the morphological properties of the femoral head. The goal of this study was to develop a method to elucidate whether these changes are localised to discrete regions, or if the reported trends in microstructural changes may be identified throughout the subchondral bone of the human femoral head. Whole femoral heads extracted from osteoarthritic (n = 5) and healthy controls (n = 5) underwent microCT imaging 39 μm voxel size. the subchondral bone plate was virtually isolated to evaluate the plate thickness and plate porosity. The trabecular bone region was divided into 37 volumes of interest spatially distributed in the femoral head, and bone morphometric properties were determined in each region. the study showed how the developed approach can be used to study the heterogeneous properties of the human femoral head affected by a disease such as osteoarthritis. As example, in the superior femoral head osteoarthritic specimens exhibited a more heterogeneous micro-architecture, with trends towards thicker cortical bone plate, higher trabecular connectivity density, higher trabecular bone density and thicker structures, something that could only be observed with the newly developed approach. Bone cysts were mostly confined to the postero-lateral quadrants extending from the subchondral region into the mid trabecular region. Nevertheless, in order to generalise these findings, a larger sample size should be analysed in the future. This novel method allowed a comprehensive evaluation of the heterogeneous micro-architectural properties of the human femoral head, highlighting effects of OA in the superior subchondral cortical and trabecular bone. Further investigations on different stages of OA would be needed to identify early changes in the bone.

Heterogeneous Strain Distribution in the Subchondral Bone of Human Osteoarthritic Femoral Heads, Measured with Digital Volume Correlation

“…The morphometric measurements for each specimen are reported in Table 1 . A detailed comparison of the morphometric properties for these OA specimens with healthy specimens can be found in Ryan et al [ 13 ].…”

“…In particular, it should be noted that the higher strains seem to localise around the heterogeneous structure of the superior femoral head. Previous studies have shown that microstructural changes within the OA femoral head lead to sclerosis and subsequent increased BV/TV in the subchondral bone with a coincident reduction in BV/TV in regions medial and lateral to the principle loading axis [ 13 ].…”

“…The illustrations shown in Figure 5 and Appendix A , however, demonstrate the large heterogeneity in architecture throughout the entire femoral head. In several specimens, the increased BV/TV and sclerotic changes in the subchondral region is associated with a decrease in BV/TV in regions medial and lateral to the mean trabecular axis [ 13 ]. The DVC outputs demonstrate that at high apparent loads, higher magnitude strains and localisations tend to occur specifically around cystic regions, or regions with lower BV/TV.…”

“…All reconstructed images were converted to 8-bit (ImageJ) [ 30 ]. For each specimen the first image acquisition dataset (Pre1) was transformed by aligning the mean trabecular direction (MTD) parallel to the supero-inferior (SI) axis in the central coronal and sagittal slices; the fovea capitis femoris was then aligned perpendicular to the antero-posterior (AP) axis on the coronal and sagittal views as described in detail in Ryan et al [ 13 ]. The Pre2 dataset was rigidly registered (Amira, v6.1) to the Pre1 image; Post1, Post 2 and Post3 data sets were then registered to Pre1 by applying the obtained transformation matrix to each of the subsequent datasets (Amira, v6.1, ThermoFisher Scientific, Ma, US).…”

“…These studies suggest that microstructurally OA trabecular bone is more heterogenous, and tends to exhibit higher values of bone volume fraction (BV/TV) and trabecular thickness (Tb.Th), combined with decreased mineral fraction, when compared to healthy specimens. However, these studies have limited the analyses to portions of trabecular bone extracted from the main structure of the femoral head, neglecting the importance of the structural connectivity of the subchondral tissue and the effect of typical morphological features common in the OA such as osteophytes, bone cysts, and sclerotic bone [ 13 ]. Moreover, extracting specimens from the main structure requires the definition of a main testing direction, limiting the information about the mechanical competence of that particular portion of the tissue under different loading scenarios.…”